6 is three times (thrice) bigger than 2 7 is bigger than 3 multiplied by 2.

If I were you, I would just use "times as large as". The problem with saying an amount "X larger than" is that not everyone will understand it the same way. It's a bit ambiguous whether you are talking about the difference or the whole amount. To see this, consider that 6 is 4 larger than 2, i.e. two times. But people won't always understand it that way, and may consider the expressions to be equivalent. It's best to avoid the potential confusion and not use that way of putting it.

6 is three times 2 (number) 7 is more than three times 2 China is 10 times larger than France. (size)

Yes, your statements are grammatically and mathematically correct.